The present invention concerns a process for working up copper cementate sludges containing arsenic which are obtained, for example, in purifying zinc solutions by means of cementation with zinc dust. Normally, these sludges contain not only copper, but also other valuable metals, especially non-ferrous metals, such as, for example, zinc, cadmium, and silver.
Working up with the aid of pyrometallurgical processes is expensive on account of the composition of these sludges which contain approximately 15-30% Cu, 10-25% Zn, and 2-6% As.
In view of the fact that the copper is present in its metallic form and in the form of arsenide, respectively, working up in the hydrometallurgical manner begins by requiring an oxidizing dissolution such as, for example, with chlorine or air, with considerable amounts of expensive oxidizing agents being required in the former case, and with the oxidizing velocity being relatively low in the latter case.